Polyvinyl alcohol compositions are known and useful for a variety of applications. For example, polyvinyl alcohol films are used in packaging materials, such as granulated laundry detergent and pulverulent pesticides and insecticides. Packages prepared from these films separate the contents from exposure to the immediate surroundings and provide premeasured amounts of the packaged materials.
Polyvinyl alcohol compositions are water soluble, and rapidly dissolve in hot water. Thus, packages with materials designed for being slurried, dispensed or dissolved in water may be conveniently added to hot water, such as to the wash water of a washing machine when the package contains a laundry aid. As the package dissolves, the contents are dispensed.
However, polyvinyl alcohol films are brittle at low temperatures and low relative humidities. They have thus not found wide commercial use as soluble films in packaging consumer products which may be stored under conditions conducive to package breakage prior to use.
U.S. Pat. No. 4,115,292, inventors Richardson et al., issued Sept. 19, 1978, discloses packets of detergent compositions in polyvinyl alcohol films which are useful in automatic dishwashers. U.S. Pat. Nos. 3,892,905, inventor Albert, issued July 1, 1975 and 4,155,971, inventor Wysong, issued May 22, 1979, both disclose polyvinyl alcohol film-forming compositions which dissolve in cold water. The former compositions are made from a polymer mixture of polyvinyl alcohol or polyvinyl pyrrolidone and a watersoluble plasticizer such as glycerol or polyethylene glycol. The latter discloses polyvinyl alcohol compositions including polyethylene glycol plasticizers which are said to impart enhanced resistance to package breakage.
U.K. patent application No. 2,090,603A, published July 14, 1982, inventor Sonenstein, discloses water soluble films comprising a uniform or homogeneous blend of water soluble polyvinyl alcohol and polyacrylic acid. The compositions are said to have high rates of solubility in both cold and hot water and to be of reduced sensitivity to humidity.
Nevertheless, the known water-soluble polyvinyl alcohol films useful as packaging or delivery pouches have continued to present problems of brittleness at low temperatures and low relative humidities.